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Message-ID: <alpine.DEB.2.02.1601041201120.19710@kaball.uk.xensource.com>
Date:	Mon, 4 Jan 2016 12:03:11 +0000
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
CC:	<linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Arnd Bergmann <arnd@...db.de>, <linux-arch@...r.kernel.org>,
	Andrew Cooper <andrew.cooper3@...rix.com>,
	<virtualization@...ts.linux-foundation.org>,
	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	David Miller <davem@...emloft.net>,
	<linux-ia64@...r.kernel.org>, <linuxppc-dev@...ts.ozlabs.org>,
	<linux-s390@...r.kernel.org>, <sparclinux@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-metag@...r.kernel.org>, <linux-mips@...ux-mips.org>,
	<x86@...nel.org>, <user-mode-linux-devel@...ts.sourceforge.net>,
	<adi-buildroot-devel@...ts.sourceforge.net>,
	<linux-sh@...r.kernel.org>, <linux-xtensa@...ux-xtensa.org>,
	<xen-devel@...ts.xenproject.org>,
	"Konrad Rzeszutek Wilk" <konrad.wilk@...cle.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	David Vrabel <david.vrabel@...rix.com>
Subject: Re: [PATCH v2 33/34] xenbus: use virt_xxx barriers

On Thu, 31 Dec 2015, Michael S. Tsirkin wrote:
> drivers/xen/xenbus/xenbus_comms.c uses
> full memory barriers to communicate with the other side.
> 
> For guests compiled with CONFIG_SMP, smp_wmb and smp_mb
> would be sufficient, so mb() and wmb() here are only needed if
> a non-SMP guest runs on an SMP host.
> 
> Switch to virt_xxx barriers which serve this exact purpose.
> 
> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>

Reviewed-by: Stefano Stabellini <stefano.stabellini@...citrix.com>

Are you also going to take care of

drivers/xen/grant-table.c
drivers/xen/evtchn.c
drivers/xen/events/events_fifo.c
drivers/xen/xen-scsiback.c
drivers/xen/tmem.c
drivers/xen/xen-pciback/pci_stub.c
drivers/xen/xen-pciback/pciback_ops.c

?


>  drivers/xen/xenbus/xenbus_comms.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/xen/xenbus/xenbus_comms.c b/drivers/xen/xenbus/xenbus_comms.c
> index fdb0f33..ecdecce 100644
> --- a/drivers/xen/xenbus/xenbus_comms.c
> +++ b/drivers/xen/xenbus/xenbus_comms.c
> @@ -123,14 +123,14 @@ int xb_write(const void *data, unsigned len)
>  			avail = len;
>  
>  		/* Must write data /after/ reading the consumer index. */
> -		mb();
> +		virt_mb();
>  
>  		memcpy(dst, data, avail);
>  		data += avail;
>  		len -= avail;
>  
>  		/* Other side must not see new producer until data is there. */
> -		wmb();
> +		virt_wmb();
>  		intf->req_prod += avail;
>  
>  		/* Implies mb(): other side will see the updated producer. */
> @@ -180,14 +180,14 @@ int xb_read(void *data, unsigned len)
>  			avail = len;
>  
>  		/* Must read data /after/ reading the producer index. */
> -		rmb();
> +		virt_rmb();
>  
>  		memcpy(data, src, avail);
>  		data += avail;
>  		len -= avail;
>  
>  		/* Other side must not see free space until we've copied out */
> -		mb();
> +		virt_mb();
>  		intf->rsp_cons += avail;
>  
>  		pr_debug("Finished read of %i bytes (%i to go)\n", avail, len);
> -- 
> MST
> 
--
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